Carburetor



Jm'zv, 1942. R. F. BRACKE 2,211, 13

CARBURETOR Filed July 21, 1958 3 Sheets-Sheet 1 Patented Jan. 27, 1942 UNITED STATES PATENT OFFICE CARBURETOR Robert F. Bracke, Chicago, Application July 21, 1938, Serial No. 220,516

12 Claims. (01261-72) My invention relates to. carburetors.

Withftheordin ary carburetor of the non-fuel lift type now in common use on automobiles and other internal combustion engines, difficulty is experienced starting" the engine when it is extremely hot. This difficulty is greatly increased when' the; carburetor is of the fuel lift type due'to thefact that the vaporization of fuel in the float bowl. of the carburetor interferes with the operation of the booster Venturi tube utilized to create a: suction in this float bowl. The resultis that the booster fails to create the usual degree of suction in the carburetor float bowl and the nozzle draws a richer than normal mixture, thereby increasing the difficulty in starting. p

Anobject of my invention is to improve both fuel lift and non-fuel lift carburetors to reduce the difliculty of starting engines equipped with such carburetors when the engines are extremely hot.

. Another object of my invention is to reduce the amount of fuel loss-through vaporization in the float bowl of the carburetor and in the fuel line connecting the float bowl with the main fuel supply tank.

Anotherobject of my invention is to reduce the deleterious effect of'vaporization of fuel in the fuel supply line leading, to the float bowl of the carburetor.

. Other objects and advantages will become apparent asthe description proceeds.

- Referring to the drawings, Figure 1 is a vertical sectional view of a fuel lift carburetor embody-- line |-l of Figure 2;."

, Figure 2 is a horizontalsection taken on the line 22 of Figure 1-; Y

-Figure3 is an. irregular vertical section taken on the line-33 of Figure 2;

1 Figure '4 is a chart indicating the quantity of gasoline distilled off for different float bowl temperatures;

Figure 5 illustrates a modification and is a vertical sectional viewof. a plain tube carburetor embodying my invention; and

Figure 6 illustrates a further modification and is a vertical sectional view of an air valve carburetor embodying my invention.

r In Figures 1 to 3 of the drawings I have illustrated a carburetor of the fuel lift type having an air inlet l0 communicating with a nozzle or fuel feeding Venturi tube l2 by way of a chamber M. The lower end of the nozzle Venturi tube [2 is located in a mixing chamber l6 which reing my invention. Thissection is taken on the ceives a secondary supply of air past the air valve l8. This air valve is supported on. a pivoted shaft andv is connected by means of arm 22 to a dashpot 24.

The lower end of the carburetor is provided with a flange 25 adapted to be secured to the intake manifold of an internal combustion engine.

trolled by means of the usual throttle valve 28.

The nozzle I2 is supplied with fuel from a float bowl which in the carburetor shown is maintained under subatmospheric pressure or suction for the purpose of drawing fuel thereinto from the main fuel supply tank commonly located at the rear of the automobile. The carburetor inlet ?2 is connected with the main fuel supply tank by the usual supply pipe which discharges the fuel into a cylindrical filter chamber 34 containing a cylindrical screen 36 through which the fuel must pass before entering the carburetor The filter chamber 34 discharges into the carburetor float bowl 30 by way of passage 38.

A tubular member 40 is threaded nto the casting forming the top of the float bowl and has a sage 5i! with a duct 54 communicating with the throat of the nozzle Venturi tube I2 by wa of vertical passage 56, annular chamber 58 and inclined passages 60 which communicate with the throat of the nozzle Venturi tube immediately below the step formed therein.

A vertical duct 62 connects the lower part of the float bowl 30 with passage 54 adjacent the plug 53. The valve 44 rests upon the upper end of a stud 64 carried on an arm 66 forming part of a sheet metal stamping 68 pivotally supported on a rod 10. A second arm 12 of the stamping 68 is attached to a float 14 which rises and falls with the level of the fuel in the float bowl and thereby controls the valve 44 whereby communication between the carburetor float bowl and the supply line is regulated.

An accelerator pump 16 is located in the bottom of the carburetor float bowl and discharges into the mixing chamber by way of duct 18 and Communication between the mixing cham-' ber l6 of the carburetor and the engine is con-- nozzle 80. The accelerator pump is operated through a rod 82 engaged by one end of a lever 04 pivoted at 86 and having an arm 80 (Figure 3) connected by a link 90 with lever 82 which is connected to the shaft 94 of the throttle valve 28. The lever 92 has an arm 98 adapted to be connected to the usual hand and foot control means located in the driving-compartment oi the automobile.

The accelerator pump rod 82 carries a plate 98 having an extension I on which is mounted a metering pin I02 provided with a tapered upper end I04 reciprocable in the metered orifice provided by a disc I06 whereby movement of the throttle valve 28 varies the freedom of communication between the nozzle Venturitube- I2 and its source of fuel supply to thereby regulate the richness of the mixture delivered by the nozzle.

The suction in the float bowl 30 is maintained by a booster Venturi tube I08 (Figure 3) which receives its supply of air through the inlet II] by way of chamber I4 and the metered orifice I I0 formed in a disc I I2. The flow of air through the booster Venturi tube I08 creates a suction in the restricted throat of this booster. This throat is in communication with the upper part of the float bowl 30 by way of radial passages II4, annular chamber H6, and duct H8.

The booster I08 discharges into a passage I20 which communicates with the mixing chamber I6 by way of duct I22 chamber I24, and inclined passage I20. The chamber I24 is intersected by a disc I28 having a metered orifice in which the tapered pin I30 of a booster control member I32 is located. The control member I32 is attached to the piston of the dashpot 24 which in turn is connected to the air valve I8 so that the shifting of this air valve varies the position of the tapered pin I30 in the orifice provided by the disc I28 to thereby regulate the degree of suction created in the carburetor float bowl by the booster I08.

In Figure 3 I have shown a choke plate I34 .which normally closes a port I36 communicating with the air inlet I0 and a second port I38 communicating with the upper end of a vertical passage I40 which opens into the booster discharge passage I20. The choke plate I34 has an arm I42 adapted to be connected to the usual dash control whereby the choke plate may be shifted to bring the elongated pocket I44 into position to establish communication between ports I36 and I38 whereby air is admitted to the booster discharge passage I20 for the purpose of re ducing flow through the booster I08. This in turn reduces the suction in the float bowl and permits the nozzle Venturi tube I2 to deliver a richer mixture to facilitate starting of a cold engine.

I have also shown this embodiment of my invention as being provided with an idling jet I46 communicating with the float bowl 30 by way of ducts I48 and I49 and the space provided between guide sleeve I50 and the tapered flat I52 formed on accelerator pump operating rod 82. The relationship of the flat I52 and guide sleeve I50 is such that when the throttle valve 28 is open through more than a third of its range communication between the idling jet I45 and the float bowl is cut off. An air inlet I54 for the idling jet I48 is located immediately above the throttle valve 28 when the latter is in closed position. The upper end of the vertical passage I48 is provided with a very fine opening I58 which prevents siphoning of the fuel from the carburetor float bowl when the engine is not operating.

My present invention is solely concerned with the arrangement of the passages connecting the float bowl of the carburetor with the fuel supply pipe and the nozzle Venturi tube I2 and the valve mechanism controlling these passageways. It is, therefore, unnecessary to describe the other features of the carburetor in detail.

It is to be understood that myinvention is particularly adapted for carburetors intended to be used with hydro-carbon fuels such as gasoline. Gasoline has no definite boiling point but is composed of many hydro-carbon compounds having difierent boiling points, and it is customary for the refineries to vary the proportions of these different hydro-carbons to adapt the fuel to different seasons of the year. Thus, in winter the commercial gasoline has a larger proportion of hydro-carbon compounds having low boiling points, whereas in summer the commercial gasoline ordinarily supplies at gasoline fllli'ng stations has a larger proportion of hydro-carbon compound having higher boiling points.

In Figure 4 I. have illustrated a chart showing the percentage of gasoline lost through vaporization for different float bowl temperatures. In

this figure I have shown the vaporization curve of both winterand summer gasoline. Ihave conducted extensive tests on a Ford V-8 automobile and found that under ordinary conditions of operation the float bowl temperature i approximately 136 F., whereas when the automobile is operated in an extremely hot climate, this-temperature may rise to F; This chart indicates that there is a very appreciable loss of gasoline through vaporization within the temperature range corresponding to actual operating conditions. A feature of my invention is the reduction of vapor loss;

In the operation .of the carburetor shown in Figures 1 to 3 inclusive the nozzle Venturi tube I2 obtains part of its'fuel supply' from the upper end of cylindrical passage 50 by way ofrestricted orifice 52 and part of its fuel supply from the bottom of the float bowl through passage 82. When the fuel level in the floatbowl drops below a predetermined height the inlet valve 44 opens; admitting fuel from the supply line through passage 42 and ports 48 into the upper end of the cylindrical passage 50. Any vapor which may have formed in the supply line passes through the restricted orifice 52 to the nozzle Venturi tube I2 and does not get into the float bowl proper. The function of the restriction 52 is to prevent vapor from being supplied to the nozzle Venturi tube I2 so fast that the nozzle will receive no liquid fuel while it is receiving vapor.

In this manner'the booster'venturi tube I08 is relieved of the necessity of withdrawing such vapor from the float bowl. Since the capacity'of the booster I08 to withdraw vapor from the float bowl is quite limited, this elimination of vapor through the nozzle Venturi tube I2 permits the booster to maintain the proper degree of suction in the float bowl at all times.

That part of the gasoline which tends to vapor- 12s in the fuel supply line comprises the hydrocarbon compounds which have the lowest boiling point, that is, the so-called light ends, so that these light ends are preventedfrom entering the float bowl proper. That part of the liquid fuel which enters the upper end of the cylindrical passage 50 and which is not immediately drawn off through the metered orifice 52 to the nozzle,

moves downwardly in the cylindrical passage 50 and displace an equal amount of fuel therebeneath into the float bowl proper until the float has been raised sufficiently to close the valve 44. Thereafter the nozzle draws fuel from the float bowl partly by way of the passage 62 and partly by way of the large cylindrical passage 50.

With mynovel arrangement of inlet valve and passages connecting the float bowl with the nozzle Venturi tube l2 and with the filter chamber and fuel supply line, a large part of the fuel entering through the valve 43, 44, is immediately carried to the nozzle Venturi tube l2 and never mixes with the fuel in the float bowl. Furthermore, the presence in the float .bowl of the downwardly projecting portion of the casting 4| which provides the large cylindrical passage 50 and the passage 62, reduces agitation of the fuel float bowl and such agitation and resulting inter-mixture of the fuel in the float bowl is further reduced by the fact that when the valve 44 is in closed position, the nozzle Venturi tube l2 withdraws part of its fuel requirements from the upper end of the large cylindrical passage 50 and the remainder through the passage 62.

Because of the relatively small admixture between the fuel in the float bowl and the incoming fuel when the valve 44 is open, the float bowl tends to become filled with gasoline from which the lighter ends have been distilled off, thereby materially reducing the rate of vaporization or distillation of the fuel in the carburetor float bowl and correspondingly reducing the loss from this cause.

The advantages of my invention are particularly noticeable when starting a hot engine. Under such starting conditions, the booster is freed from the necessity of taking care of the large amount of vapor which has heretofore collected in the carburetor float bowl while the hot engine was standing idle. By thus freeing the booster of such excessive vapor, the booster is capable of functioning normally and produces the normal degree of suction in the carburetor float bowl. This means that the nozzle Venturi tube I 2 draws only th normal amount of fuel to produce the starting mixture instead of providing the excessively rich mixture produced by the prior art carburetors. The idling jet I46 would also be prevented in the same manner from producing an abnormally rich mixture except thatunder most starting conditions the throttle Valve is open wide enough to cut off the idling jet from the float bowl. f

A further economy is effected by the fact that any vapor formed in the fuel supply line and fllter chamber is drawn directly into the nozzle Venturi tube I2 where it is mixed with the primary .air to form a combustible mixture and thus utilized to accomplish useful work. In the prior art carburetors such vapor was not only wasted, but served to unduly enrich the mixture and thus promote the formation and deposit of carbon in the engine cylinders.

While my invention is particularly useful in carburetors of the fuel lift type, my invention also has advantages when applied to carburetors of the non-fuel lift type.

In Figure 5 I have illustrated my invention as applied to a non-fuel lift carburetor of the plain tube type. This carburetor has an air inlet 200 provided with the usual choke valve 202. The inlet 200 directs the air into a Venturi-shaped mixing chamber 204 communicating with a throttle bore 206 having the usual throttle valve 208. It will be understood that the flange 2) at the lower end of the throttle bore is provided for attaching the carburetor to the inlet manifold of an internal combustion engine.

The carburetor is connected with the main fuel supply tank by a supply line (not shown) adapted to be connectedto the inlet nipple 2|2 leading to the filter chamber 2l4 containing the cylindrical screen 2| 6 attached to a removable plug 2I8. After the gasoline has passed through the screen 2I6, it flows through horizontal passage 220 to the vertical passage 222 formed in a hollow plug 224 forming a seat for th float controlled valve 226. The valve 226 has a section 228 of triangular cross-section which is guided in the large cylindrical passage 230 formed by a depending part of the. casting 232 which forms the top of the float bowl 234. The lower end of the valve 226 rests upon a lever 236 pivoted at one end at 238 and having its other end attached to the float. 240.

The upper end of the large cylindrical passage 230 communicates by way of restricted orifice 242 with passage 244 leading to the main fuel feeding nozzle 24B and also to the idling jet 248 which is controlled'by an'adjustable needle valve 250. The passage 244 also communicates with the interior of the float bowl 234 by way of vertical duct 252. The float bowl is maintained under atmospheric pressure by means of a vent 254.

In the plain tube carburetor of Figure 5 the main nozzle 246 and the idling jet 248 draw part of their fuel from the upper end of the large cylindrical passage 230 through restricted orifice 242 and the remainder of their fuel from the float bowl through passage 252. When the level of the fuel in the float bowl drops, the valve 226 opens and additional fuel is supplied to the float bowl either by gravity flow or by a fuel pump or any other suitable means. Any vapor which may have formed in the fuel supply line never enters the float bowl proper but is drawn immediately to the nozzle 246 by way of restricted orifice 242 where it is mixed with air and utilized to operate the engine instead'of being lost by way of the atmospheric vent 254.

Because of my novel arrangement of passages, there is relatively little fl'ow of fuel into and out of the float bowl and relatively little mixing between the fuel in the float bowl and fuel admitted through the port controlled by the float valve 226. Such lighter ends as may be present in the gasoline in the float bowl are vaporized or distilled off in the usual manner and lost through the vent 254 but thereafter little loss through vaporization or distillation occurs since the lighter ends are either drawn directly to the nozzle while the float valve is open or remain in the large vertical passage 23!! and never reach the float bowl proper. efliciency of the carburetor due to the smaller loss because of vaporization and distillation, this carburetor has the advantage of providing easier starting when the engine is hot.

In Figure 6 I have shown my invention applied to what may otherwise be considered as atypical air valve carburetor of the non-fuel lift type. This carburetor is provided with an air inlet 300 which communicates with the mixing chamber 302 by way of nozzle Venturi tube 364 and also past secondary air valve 306 when the latter is open. This air valve is pivoted at 308 and is connected by link MD with a slide 3l2 pressed in valve closing direction by a spring 3|4 seated In addition to the greater upon the head'3l6 of a sleeve 318. 3 l 8 may slide within the limits permitted by stop shoulders 32.!) and 322 and may be adjusted to any desired position within these limits as by means of lever 324 adapted to be connected with the choke control on the dash of an automobile.

The lower end of the carburetor is provided with a flange 328 for attachment to the intake manifold of an automobile and the usual throttle valve 328 is provided to control communication between the mixing chamber 302 and the intake manifold. An idling jet 330 controlled by an adjustable needle valve 332 is located on the engine side of the throttle valve 328.

The carburetor is provided with an inlet nipple 334 adapted to be connected with an elevated tank or fuel pump by means of a suitable supply pipe not shown. Before entering the float bowl of the carburetor, the fuel passes into the filter chamber 336 through the wire screen 338 carried by the removable plug 340 and, into chamber 342 before entering the carburetor float bowl 344.

Admission of fuel to the float bowl 344 is controlled by a valve 346 having a triangular portion 343 guided in a large cylindrical passage 350 opening at its lower end into the float bowl 344. Fuel entering past the valve 346 flows into the upper end of the passage 350 and part of this fuel, including any vapor contained therein, passes directly to the nozzle and idling jet by way of restricted orifice 352 and passages 354 and 356. Part of their requirements are also supplied from the float bowl by way of vertical duct 358.

The float 360 is pivotally connected to the pin 362 by means of a lever 364 which underlies the valve 34% whereby the position of the float controls the position of this valve and regulates the admission of fuel to the float bowl. In so faras my present invention is concerned, the operation of the carburetor of Figure 6 is similar to that of Figure and need not be described.

It is to be understood that my invention is not limited to the particular forms illustrated and described, but may assume various forms and that the scope of my invention is limited solely by the following claims.

I claim:

1. A fuel lift carburetor of the class described comprising a float bowl, a fuel feeding nozzle supplied with fuel from said float bowl, a float bowl top having a part extending downwardly into said float bowl, said part providing a large downwardly extending passage communicating with the interior of said float bowl at its lower end, an inlet valve connecting the upper end of said passage with a fuel supply line, a float controlling said inlet valve, a restricted connection between the upper end of said passage and said nozzle, said part providing a smaller downward- 1y extending passage opening at its lower end into said float bowl and having its upper end in communication with said nozzle, and means for creating suction in said float bowl, said means communicating with said float bowl at a point spaced from said downwardly extending passages.

2. A fuel lift carburetor of the class described comprising a float bowl, a fuel feeding nozzle supplied with fuel from said float bowl, means providing a large downwardly extending passage communicating with the interior of said float bowl at its lower end, an inlet valve connecting the upper end of said passage with a fuel supply line, a float controlling said inlet valve,

The sleeve a restricted connection between the upper end of said passage and said nozzlfi, means providing a smaller downwardly extending passage open: ing at its lower end intov said float bowl and hav-. ing its upper end in communication with said nozzle, and means for creating suction in said float bowl, said means communicating with said float bowl at a point spaced from said downwardly extending passages.

3. A fuel lift carburetor of the class described comprising a fuel bowl, a fuel feeding nozzle supplied with fuel from said bowl, means pro.- viding a large downwardly extending passage communicating with the interior of said bowl at its lower end, an inlet valve connecting the upper end of said passage with a fuel supply line, means controlling said inlet valve, a restricted connection between the upper end of said passage and said nozzle, means providing a smaller downwardly extending passage opening at its lower end into said float bowl and having its upper end in communication with said nozzle, and means for creating suction in said bowl, said means communicating with said, bowl at a point spaced from said downwardly extending passages.

4. A fuel lift carburetor of the class described comprising a float bowl, 9. fuel feeding nozzle supplied with fuel from said float bowl, a float bowl top having a part extending downwardly into said float bowl, said part providing a large downwardly extending passage communicating with the interior of said float bowl at its lower end, a valve seat threaded into said part and connecting the upper end of said passage with a fuel supply line, a valve engaging said seat, said seat having a part for guiding said valve, a float controlling said inlet valve, a restricted connection between the upper end of said passage and said nozzle, said part providing a smaller downwardly extending passage opening at its lower end into said float bowl and having its upper end in communication with said nozzle, and means for creating suction in said float bowl, said means communicating with said float bowl at a point spaced from said downwardly extending passages.

5 A fuel lift carburetor of the class described comprising a float bowl, a fuel feeding nozzle supplied with fuel from said float bowl, a float bowl top having a part extending downwardly into said float bowl, said part providing a large downwardly extending passage communicating with the interior of said float bowl at its lower end, an inlet valve connecting the upper end of said passage with a fuel supply line, a float controlling said inlet valve, said part providing a smaller downwardly extending passage opening at its lower end into said float bowl and having its upper end in communication with said nozzle, a restricted connection between the upper ends of said passages, and means for creating suction in said float bowl, said means communicating with said float bowl at a point spaced from said downwardly extending passages.

6. In a carburetor, the combination of a nozzle, a float bowl from which said nozzle is supplied with fuel, means extending downwardly into said float bowl and providing a pair of passages, one of said passages having a tubular member at its upper end providing a valve seat, a valve for said seat, said valve located in said passage and being guided thereby, said valve member being of smaller cross-section than said passage, whereby flow through said passage is permitted, a float for controlling said valve, means providing restricted communication between the upper end of said passage and said nozzle, means providing free communication between the upper end of said other passage and said nozzle, and means providing an atmospheric vent for the float bowl.

7. In a carburetor, the combination of a nozzle, a float bowl from which said nozzle is supplied with fuel, means extending downwardly into said float bowl and providing a pair of passages, one of said passages having a tubular member at its upper end providing a valve seat, a valve for said seat, said valve located in said passage and being guided thereby, said valve member being of smaller cross-section than said passage, whereby flow through said passage is permitted, a float for controlling said valve, means providing restricted communication between the upper end of said passage and said nozzle, and means providing free communication between the upper end of said other passages and said nozzle.

8. In a fuel lift carburetor, the combination of a nozzle, a float bowl from which said nozzle is supplied with fuel, means extending downwardly into said float bowl and .providing a pair of passages, one of said passages having a tubular member at its upper end providing a valve seat, a valve for said seat, said valve located in said passage and being guided thereby, said valve member being of smaller cross-section than said passage, whereby flow through said passage is permitted, a float for controlling said valve, means providing restricted communication between the upper end of said passage and said nozzle, means providing free communication between the upperend of said other passage and said nozzle, and means for maintaining suction in said float bowl.

9. In a carburetor the combination of a nozzle, a float bowl from which said nozzle is supplied with fuel, a top for said float bowl having a part extending downwardly into said bowl and providing a pair of passages opening at their lower ends into said bowl, valve means at the upper end of one of said passages for connecting said passage with a fuel supply line, a restricted communication between the upper ends of said passages, a duct connecting the upper end of the other passage with said nozzle, and a float for operating said valve.

10. In a carburetor the combination of a nozzle, a bowl from which said nozzle is supplied with fuel, means providing a pair of downwardly-extending passages opening at their lowerends into said bowl, valve means at the upper end of one of said passages for connecting said passage with a fuel supply line, a restricted communication between the upper ends of said passages, a duct connecting the upper end of the other passage with said nozzle, and means for operating said valve.

11. In a fuel lift carburetor the combination of a nozzle, a float bowl from which said nozzle is supplied with fuel, a top for said float bowl having a part extending downwardly into said bowl and providing a pair of passages opening at their lower ends into said bowl, valve means at the upper end of one of said passages for connecting said passage with a fuel supply line, a restricted communication between the upper ends of said passages, a duct connecting the upper end of the other passage with said nozzle, a float for operating said Valve, and means for maintaining suction in said float bowl.

12. In a carburetor the combination of a nozzle, a float bowl from which said nozzle is supplied with fuel, a top for said float bowl having a part extending downwardly into said bowl and providing a pair of passage-s opening at their lower ends into said bowl, valve means at the upper end of one of said passages for connecting said passage with a fuel supply line, a restricted communication between the upper ends of said passages, a duct connecting the upper end of the other passage with said nozzle, a float for operating said valve, and means providing an atmospheric vent for said float bowl.

ROBERT F. BRACKE. 

